Dossier - Impact of Personal Privacy Devices on Global Navigation Satellite System
Magazine Article / November 7, 2013 / Project number: 2013 - Issue 3
By Lieutenant-Colonel (Ret’d) Sean Murphy, former DG Space Requirements – GNSS/NAVWAR, NDHQ Ottawa
LCol Murphy joined the RCAF in 1973. During his 40 year career, he served as a tactical helicopter pilot with 427 Sqn Petawawa, 444 Sqn Lahr Germany, and 408 Sqn Edmonton flying both the CH135 and 136 helicopters. He also held various staff positions with the Royal Canadian Air Force (RCAF) and strategic staff with notable tours as A3 Contingency Ops Staff at AirCom HQ Winnipeg, Career Manager, ISR domain manager for the CAF, and most recently as the Navigation Warfare Program Director for the RCAF. LCol Murphy retired from the RCAF on 2 June 2013.
Advancements in Global Navigation Satellite System (GNSS) technologies continue to drive new and evolving GNSS applications. These applications are proliferating exponentially as the technologies are further integrated into mass-market consumer products. For the public sector, significant benefits are being realized thanks to the capacity of GNSS to support vital terrestrial operations in aviation, tracking, timing, geomatics, navigation and search and rescue, to name just a few. The international community, including the United Nations, recognizes the ubiquity of GNSS and the vast implications to society, economics and development globally. To date, the world has mainly relied on the Global Positioning System (GPS). It has been estimated the direct economic benefits of GPS technology in Canada to be in the $6-7 billion range and possibly as much as 6-7% of Canada’s GDP may be dependent on GPS (approximately $95 billion).1 Other nations have or soon will be fielding their own GNSS systems. Unfortunately, GNSS is deemed vulnerable due the availability of inexpensive hardware capable of jamming incoming GNSS signals.
Militarily, GPS has become critical to all aspects of modern CF military operations (PGMs, navigation, precise timing). To protect US/Allied access to GPS and prevent adversary use of GPS, while minimizing the impact outside the areas of operations, the U.S. DoD initiated the Navigation Warfare (NAVWAR) program in 1996. The Canadian NAVWAR Program Office was established in 2002 to be the focal point within DND and the CAF to coordinate, administer and oversee the Canadian NAVWAR activities. The NAVWAR program’s main objectives are to evaluate and mitigate vulnerabilities to CAF operational platforms and systems, which include fully understanding the implications of intentional or unintentional disruption of the military and civil use of the GNSS signals, specifically the GPS signal.
The civil aviation sector is increasingly moving towards a reliance on GNSS technology in order to facilitate the flow of air traffic and to reduce the costs of maintaining land-based infrastructure. Additionally, the air transportation industry is continuously evaluating risk and mitigation strategies of GNSS technology to make the aviation sector as safe as possible. The strategies include the following:
- Three WAAS satellites provide a high level of redundancy over most of Canada.
- Appropriate levels of ground-based navigation aids are being maintained to support flight operations.
- A useable approach completely independent of GPS at either the destination or alternate airport is required.
- Simulation exercises are held to assess the increase in controller workload resulting from a widespread GPS outage, and to train ATC personnel to handle such outages.
- NOTAM alerting of WAAS and/or GPS outages is provided.
- FAWP crossing altitudes are published on approach plates so that pilots can validate the vertical guidance.
- GPS and WAAS performance is continuously monitored.
- Procedures are checked for GPS/WAAS satellite masking and flight checking of GPS/WAAS approaches is conducted before publication.
The illegal use of GPS jammers, often referred to as Personal Privacy Devices (PPDs) or Radio Jamming Devices (RJDs) that interfere with the GPS signal, is growing in Canada and throughout the world. The typical PPD device is usually poorly designed and constructed with the result that they impact a much greater area than intended (most jammers have a range of 100 m to 1 km, however, some may have an effective range up to 10 km). The proliferation of these inexpensive devices has the very real potential to interfere with RNAV approaches at airports.
There have been a number of incidents in Canada and other countries involving PPDs that have caused disruption to the use of GNSS in aviation. Here are a few examples:
- Newark Airport. In late 2009, engineers noticed that satellite-positioning receivers for a new navigation aid at Newark Liberty International Airport in New Jersey were suffering brief daily breaks in GPS reception. Over a period of several weeks, sporadic outages of the GPS Ground-Based Augmentation System (GBAS), located at the airport to provide precision approach services, occurred due to radio-frequency (RF) interference from unknown sources. Analysis showed that certain vehicles on a nearby freeway were the likely culprit(s), and using advanced interference detection equipment and multiple surveillance cameras, an offending truck driver was caught and arrested. In his possession was a widely available $33 GPS jammer.2
- Chibougamau Leg Bracelet. Periodic GPS interference problems were affecting aviation operations at the Chibougamau/Chapais Airport, located approximately 20 km southwest of Chibougamau, Quebec. With the assistance of Industry Canada’s Spectrum, Information Technologies and Telecommunications (SITT) Sector radio-communications interference detection technology, and after several weeks of investigation, the source was identified. An offender, who was wearing a GPS ankle monitor as part of court-imposed movement restrictions, was jamming it in order to visit his girlfriend who lived outside his prescribed area of movement. Coincidentally, his travel route brought him into close proximity of the airport.3
- Edmonton Airport. On 6 and 7 December 2012 and at approximately the same geographic point, GPS signals were reportedly lost by separate aircraft conducting the RNAV runway 20 approach at CYEG. The pilot, who was the same in both incidents, experienced the signal losses flying different aircraft each night. The first night, the signal was lost on both the Universal FMS and the Garmin 400 GPS. The Universal reported “Position uncertain” and the Garmin simultaneously reported “Poor GPS coverage.” The next night at about the same point on the approach, the FMS went haywire and reported “Position uncertain,” reacquiring position a minute or two later just before reaching the airport. The fact that it happened in two different aircraft, with three different GPS units made it fairly certain that was not an equipment problem. Also, a Learjet conducting the approach was observed to be off course on final approach but landed without incident. When queried, after landing, the Learjet pilot confirmed he had done the RNAV approach and had lost GPS signal during the approach. Industry Canada investigated and was able to geo-locate the interference to a strip mall close to the approach path. While interviewing persons at the mall, the signal stopped transmitting.4
- Industry Canada Trials. Industry Canada has been conducting trials since November 2012 to determine the extent of the problem of GPS signal interference by PPDs near Canadian airports. Over the course of 13 days, they had 51 jamming instances. The lengths of these occurrences were short, suggesting that they were being used by transiting vehicles. Not all signals detected were strong enough to impact the GPS approach to the airport, but some were powerful enough to interfere with the signal.5
In the military, we have the advantage that we carry (for most airframes) military GPS receivers that provide quite a bit of signal protection as long as the receivers are keyed; an un-keyed military receiver provides no added protection. Additionally, most of our aircraft equipped with military GPS receivers, have or will soon have GPS anti-jam antennae systems, adding additional capability protection. Unfortunately, for the most part, the military receivers used by the RCAF are not yet authorized for use when operating in Canadian civilian airspace, which means the installed civilian GPS receivers must be used, making them vulnerable to interference from PPDs.
Both Industry Canada and the Department of Justice are looking at updating both the Radiocommunications Act and the Criminal Code of Canada to address PPDs and other interference devices. In the meantime, aircrew must remain vigilant to this very real vulnerability and avoid complacency as GNSS use becomes more pervasive in our daily lives and impacts our economy. Don’t be caught unaware, follow the established procedures that deal with the loss of satellite reception when conducting RNAV approaches and always have a back-up approach dialled up and ready to go.
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